Dye leveling with znsox on textiles of



United States Patent 3,123,432 DYE LEVELING WITH ZnS0 ON TEXTILES 0F POLYACRYLONITRELE COPOLYMERS AND BLENDS Myron Q. Webb, Wilmington, Del., assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Sept. 22, 1961, Ser. No. 139,869 4 Claims. (Cl. 821) This invention relates to a process for dyeing with basic dyestuffs textile fibers prepared from acrylonitrile polymers having a large number of anionic groups on the polymer chain and to a process for union dyeing textile fibers prepared from acrylonitrile polymer compositions which differ in anionic group content.

It is known that in dyeing acrylonitrile polymer fibers basic dyestuffs can be used. The dyeings obtained are generally even in shading and have good fastness properties. Difiiculty has been encountered, however, in obtaining good level dyeing in fibers prepared from acrylonitrile polymers having a large number of anionic groups, i.e., sulfate and sulfonate substituents, on the polymer chain. Non-uniformities appear due to the rapid exhaustion of the dyestuflf from the bath. Even more difiiculties occur in the union dyeing of blends of fibers having low and high anionic group contents. A particularly difiicul-t problem has been encountered in the dyeing of composite fiber structures in which dissimilar polymeric compositions extend in side-by-side relationship along the length of the fiber. While a great number of dye retarders for basic or cationic dyestuffs are known, e.g., long chain alkyl quaternary amine salts, such retarders are not effective in the union dyeing of slow dyeing and fast dyeing acrylonitrile polymer fibers or composite fiber structures containing the different polymeric components since they reduce the dye pickup of both components.

It is, therefore, an object of this invention to provide a process for level dyeing with basic dyestuffs acrylonitrile polymer fibers having a high anionic group content. It is another object of this invention to provide level union dyeing of blends of fibers prepared from acrylonitrile polymers having diiierent anionic group contents. A further object of this invention is to provide a process for level dyeing composite fibers by reducing the dyeing rate of the component having a high anionic group content without substantially afiec-ting the dyeing rate of the component having a lesser anionic group content.

A still further object of this invention is to provide a' process for level dyeing of composite fibers when using usual dyeing procedures. Other objects of this invention will appear hereinafter.

The objects of this invention are accomplished by dyeing acrylonitrile polymer fibers with a basic dyestuff in the presence of Zinc or magnesium sulfate. It has been found that the inclusion of a small amount, e.g., as little as 0.5% based on the weight of the fiber to be dyed, of

the salt in the bath reduces the rate of dyeing of acrylonitrile polymer fibers having about 60 or more milliequivalents per kilogram of polymer of anionic groups on the polymer chain to approximately the same level as that for acrylonitrile polymer fibers having a lesser number of anionic groups on the polymer chain. Surprisingly, the zinc and magnesium salts have little or no effect on the dye pickup rate of acrylonitrile fibers containing less than 60 milliequivalents per kilogram of such groups on the polymer chain.

By the expression milliequivalents per kilogram of polymer of anionic groups it is meant the number of milliliters of 1N alkali which would be required to neutralize the combined sulfonate and sulfate substituents in 3,123,432 Patented Mar. 3, 1964 a kilogram of polymer if all such substituents were in the free acid form.

In practicing this invention, the zinc and magnesium salts are used in an amount from about 0.5% to about Ordinarily, amounts from about 2% to about 4%, based on the weight of the fiber to be dyed, are preferred, with amounts above 4% not being required. The bath is generally prepared at room temperature and the fibers or fabrics to be dyed are immersed in the bath. The bath is then raised to the boil at a predetermined rate with the dyeing proceeding for a selected period of time.

The acrylonitrile polymer fibers having a large number of anionic groups on the polymer chain may be prepared by known methods. Copolymers containing a broad range of sulfate and sulfonate groups are disclosed in US. 2,837,500 and 2,837,501. Generally, the polymer contains a major proportion of acrylonitrile, a small percentage of an ethylenically unsaturated copolymerizable monomer which provides the anionic groups such as ethylenically unsaturated sulfonic acids and their watersoluble salts, and a minor proportion of a neutral ethylenically unsaturated monomer which is copolymerizable with acrylonitrile. The inclusion of the neutral monomer is optional and, accordingly, it may be omitted. The anionic groups which serve as the primary dye sites may be provided from a redox polymerization initiator system such as the persulfate/bisulfite system disclosed in US. 2,462,354, as well as by copolymerization with a monomer containing the anionic groups.

Preferred embodiments of the invention are illustrated in the following examples in which proportions are given in parts by weight unless otherwise specified.

Example I viscosity of 2.00 and contained about 26 milliequivalents of anionic groups per kilogram of polymer. In preparing fiber A, dimethylformamide solutions of the two polymers were dry spun to provide about 50% of each of the polymer solutions to each hole of a multi-orifice spinneret.

The resulting composite filaments were drawn to four times their original length in baths of water at C. which extracted the residual solvent. The substantially solvent-free fiber was then mechanically crimped, cut into staple fiber of such a length as to yield a 2" dry cut length after relaxation. The staple was then dried in a circulating air oven at 270 F. to 275 R, which reduced residual shrinkage potential in boiling water to less than 3%.

A fiber B was prepared from a terpolymer comprised of 93.63% acrylonitrile, 6% methyl acrylate, and 0.37% sodium styrenesulfonate. The terpolymer had an in trinsic viscosity of 1.50 and contained about 54 milliequivalents per kilogram of polymer on the polymer chain. The terpolymer was dry spun from a dimethylformamide solution to provide a single component fiber. Staple fibers were prepared as described for fiber A.

Both groups of staple fibers were cotton-system spun to provide 30/1 cotton count yarns. The yarns obtained were then knitted on a circular knitting machine, four courses of one alternating with four courses of the other,

to give a composite fabric. Since the yarns prepared from the composite fibers become bulky when immersed in boiling water, the two types of fibers could be readily identified in the fabric. By this means it was possible to make a direct dye pickup comparison between these two fibers.

Example [I For each 100 parts of fabric to be dyed, 4000 parts of an aqueous bath was prepared at room temperature to contain the following:

0.25 part Basic Blue dye, C.I. N0. 21

0.5 part glacial acetic acid 0.5 part of a levelling agent composed of a non-ionic condensation product of ethylene and propyleneoxides 10.0 parts of Glaubers salt (calculated as anhydrous Na SO 1.0 part of a retarder comprising a quaternary amine salt derived from naturally occurring fats.

A fabric prepared as described in Example I was added to the bath and the bath was then raised slowly to the boil, the rate of temperature increase being approximately 2 F. per minute. After reaching the boil, the bath was maintained at the boil for an additional one and onehalf hours and then cooled to approximately 120 F. The bath was then removed and the dyed fabric rinsed with warm water. The fabric had developed a distinct ribbed effect as a result of the alternating bi-component and homo-fiber yarns which were used to make up the fabric, the bi-component yarns, being substantially more bulky than the homo-fiber yarns, giving a sculptured surface effect.

The marked difference in dye receptivity between thesetwo types of fiber was clearly evident in a substantially deeper shade of blue on the bulky or bi-component stripes in the fabric relative to the homo-fiber stripes. The difference in dye level was approximately eight shades as estimated by comparison with standards; one-half shade on this scale is the minimum detectable difference. The presence of a powerful quaternary amine salt retarding agent was not effectual in levelling the difference in dye receptivity between these two fibers.

In a second experiment, an alternative retarder, a longchain alkyl quaternary amine salt, was substituted for the fatty acid quaternary amine salt of this example. Since it is known that the alkyl quaternary salt was only one third as effective as the fatty acid quaternary salt, three parts of said alternative retarder was used. Substantially the same results as those obtained using the fatty acid quaternary salt were obtained.

Example III A dye bath was prepared as described in Example II except that four parts of zinc sulfate (anhydrous) were added.

Using the proportions of fabric to dye bath and the procedure described in Example 11, a sample of the composite fabric was dyed. While the distinct ribbed effect noted previously was also developed in this fabric, there was no evidence of a difference in degree of dye pickup, which means the two fibers were dyed to within one-half shade of the same. The single-component fiber had dyed to the same depth as had the bi-component, rapidly dyeing fiber. Thus, it was shown that the presence of 4% zinc sulfate had accomplished a selectivity in retardation of dye pickup rate of the bi-component fiber.

Example IV A dye bath was prepared as described in Example III except that the zinc sulfate was reduced from four parts to two parts. A sample of the composite fiber described in Example I when dyed in this bath showed slight but discernible differences in rate of dye pickup between the bi-component and the single component fibers, indicating that the concentration of the zinc sulfate can be varied to produce various shadings in such fabrics.

Example V A dye bath was prepared as described in Example IV except that anhydrous magnesium sulfate, four parts, replaced the four parts of Zinc sulfate used in that example. A sample of the composite fabric, when dyed in this bath, according to the procedure outlined in Example II, showed slightly less dye pickup in the bi-component fiber than in the homo-fiber, indicating that a slightly greater selective retardation is achieved when using magnesium sulfate. When the experiment was repeated using 3.5 parts of magnesium sulfate, no shade differential was noted.

Example VI A bath was prepared as described in Example III except that the zinc sulfate was replaced by four parts of aluminum sulfate (anhydrous). A sample of the composite fabric, when dyed in this bath, showed the same marked differences in dye shading as between the two types of fiber illustrated in Example II, indicating that no retardation is provided by presence of the aluminum salt.

Example VII For each parts of fabric to be dyed, 4000 parts of an aqueous solution was prepared at room temperature to contain the following:

0.25 part Basic Blue dye, C.I. No. 21

0.5 part glacial actic acid 0.5 part levelling agent as described in Example II 5.0 parts retarder as described in Example II 20 parts Glaubers salt (calculated as anhydrous Na SO A composite fabric prepared as described in Example I, when dyed in this bath, showed severe depth-of-shade striping, indicating no substantial improvement over the control of Example II, despite the large increase in quantity of retarder and Glaubers salt.

Example VIII One part by weight of staple fiber A and three parts by weight of staple fiber B, described in Example I, were blended in a picker feed hopper and processed on standard cotton system equipment to yield a 30/1 cotton count yarn. This yarn was then knitted on a circular knitting machine. The resulting fabric was dyed according to the procedure described in Example II. The fabric had a heather appearance.

A second sample of the knitted fabric was dyed according to the process described in Example V as modifiedto contain only 3.5 parts of magnesium sulfate. In this case, there remained no evidence of a differential in dye receptivity of the two fibers, the dye pickup rate having been leveled completely.

Example IX This example will illustrate the benefit of the magnesium or Zinc ion dyeing technique in the dyeing of single component fiber yarns and fabrics comprising polymers having high acidic function content.

A staple yarn made from polymer containing 97% acrylonitrile and 3% potassium ethylene sulfonate (206 milli-equivalents of anionic groups per kilogram of polymer) was dyed in the manner described in Example II. Dye pickup rate was excessively high as evidenced by a nonuniform appearance.

A second sample of this fabric was dyed according to the procedure outlined in Example III. The fabric was dyed to a uniform shade.

As illustrated in the foregoing examples, by utilizing zinc or magnesium sulfate in the dye bath, level dyeing is achieved for both high anionic content fibers as well as in the union dyeing of high and low anionic content fibers. Since the dye receptive groups in both types of fibers are of the same general type, the selective afiinity exhibited by the zinc and magnesium salts for the fiber containing the greater number of anionic groups is not fully understood. While the degree of retardation in dye rate appears to be dependent, within limits, on the quantity of the salt present in the dye bath, the optimum amounts can be readily selected for the particular fibers being dyed.

The dye bath may contain the usual adjuvants utilized in dyeing acryonitrile polymer fibers in addition to the zinc or magnesium sulfate. The basic dye utilized is not critical and may be selected from such W6ll-kl1OWI1 dyes as those disclosed, for example, in US. 2,891,835.

Fibers prepared from numerous other acrylonitrile polymer compositions may be dyed in the same manner as described in the examples. Preferably, the acrylonitrile polymers will contain at least 85% combined acrylonitrile. In addition to the neutral monomers disclosed in preparing the copolymers, other well-known copolymerizable ethylenically unsaturated monomers, such as those described in US. 2,436,926, may be utilized. Generally the neutral monomers may be present in an amount up to about 15% by weight of the polymer. The monomers providing the anionic groups on the polymer chain are generally utilized in amounts from about 1% to about 10% by Weight of the copolymer. Among the monomers providing such groups are the ethylenically unsaturated sulfonic acids such as styrene sulfonic acid, methallyl sulfonic acid, allyl sulfonic acid, and ethylene sulfonic acid and their Water-soluble salts.

The process of the present invention has its greatest utility in dyeing blends and composite fibers prepared from acrylonitrile polymers and copolymers having a substantial differential anionic group content. Composite or multiple component fibers prepared from such polymers and copolymers are disclosed in French Patent 1,205,162. It is to be understood, however, that other natural and synthetic fibers having dye characteristics similar to those exhibited by acrylonitrile polymer fibers containing less than about 60 rnilliequivalents per kilogram of polymer of anionic groups on the polymer chain may be union dyed with the acrylonitrile polymers fibers by the process described herein.

As many Widely different embodiments of this invention may be made Without departing from the spirit and scope thereof, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims.

I claim:

1. A process for level dyeing of a fabric of a copolymer of acrylonitrile which comprises immersing a fabric of copolymer of acrylonitrile and an ethylenically unsaturated compound having a member of the group consisting of a sulfate and sulfonate radical, said radicals being present in the polymer to the extent of milliequivalents to about 600 milliequivalents per kilogram to an aqueous bath containing a basic dyestufi and zinc sulfate, said zinc sulfate being present in an amount from about 0.5% to about 20% by weight based on the Weight of the fibers to be dyed.

2. The process of claim 1 wherein said acrylonitrile polymer is comprised of at least acrylonitrile, from about 1% to about 10% of a copolymerizable monomer selected from the class consisting of ethylenically unsaturated sulfonic acids and their water-soluble salts, and from 0% to about 14% of another copolymerizable ethylenically unsaturated monomer.

3. The process of claim-l wherein said fibers are com posite fibers which are unitary in cross section with said dissimilar polymeric compositions extending side-by-side the entire length of the fiber.

4. The process of claim 1 wherein said dissimilar polymeric compositions comprise separate fibers.

References Cited in the file of this patent UNITED STATES PATENTS 2,741,605 Zwilgmeyer Apr. 10, 1956 2,822,385 Estes Feb. 4, 1958 FOREIGN PATENTS 590,970 Canada Jan. 19, 1960 OTHER REFERENCES Diserens: Chemical Technology of Dyeing and Printing, vol. II, 1951, pages 137-140, published by Reinhold Publishers.

Diserens: Chemical Technology of Dyeing and Printing, vol 2, pages 527-528, publ. by Reinhold Publ. Corp., New York.

Cohen et al.: American Dyestufi Reporter, pages 325328, May 19, 1958.

The Textile Manufacturer, November 1959, page 517. 

1. A PROCESS FOR LEVEL DYEING OF A FABRIC OF A COPOLYMER OF ACRYLONITRILE WHICH COMPRISES IMMERSING A FABRIC OF COPOLYMER OF ACRYLONITRILE AND AN ETHYLENICALLY UNSATURATED COMPOUND HAVING A MEMBER OF THE GROUP CONSISTING OF A SULFATE AND SULFONATE RADICAL, SAID RADICALS BEING PRESENT IN THE POLYMER TO THE EXTENT OF 60 MILLIEQUIVALENTS TO ABOUT 600 MILLIEQUIVALENTS PER KILOGRAM TO AN AQUEOUS BATH CONTAINING A BASIC DYESTUFF AND ZINC SULFATE, SAID ZINC SULFATE BEING PRESENT IN AN AMOUNT FROM ABOUT 0.5% TO ABOUT 20% BY WEIGHT BASED ON THE WEIGHT OF THE FIBERS TO BE DYED. 